Prostaglandin D2 (PGD2) is a metabolic product of arachidonic acid through PGG2 and PGH2, and known to have various potent physiological activities. For example, in Non-Patent Document 1 it is described that PGD2 is involved in sleeping and secretion of hormones in central nervous system, and in inhibiting activity of platelet aggregation, contraction of bronchial smooth muscle, vasodilation and constriction of a blood vessel etc. in peripheral system. Moreover, PGD2 is considered to be involved in forming pathological condition of an allergic disease such as bronchial asthma since it is a major metabolic product of arachidonic acid produced from a mast cell, and has a potent bronchoconstricting effect, causing an increase of vascular permeability and migration of inflammatory cell such as eosinophils.
A DP receptor (also called DPI receptor) or CRTH2 receptor (also called DP2 receptor) is known as a receptor of PGD2 but these are completely different receptors. WO2007/029629 (Patent Document 1) discloses indazole compounds etc. having DP receptor antagonistic activity but does not describe the compounds as having CRTH2 receptor antagonistic activity. Similarly, WO2007/010964 (Patent Document 2) discloses indole derivatives having DP receptor antagonistic activity, and WO2007/010965 (Patent Document 3) discloses azaindole derivatives having DP receptor antagonistic activity, but neither document describes the indole or azaindole derivatives as having CRTH2 receptor antagonistic activity.
On the other hand, WO2003/097598 (Patent Document 4) discloses indazole compounds having CRTH2 receptor antagonistic activity but does not describe the compounds as having DP receptor antagonistic activity. Similarly, WO2005/123731 (Patent Document 5) discloses azaindole derivatives having CRTH2 receptor antagonistic activity, and WO2006/034419 (Patent Document 6) discloses indole derivatives having CRTH2 receptor antagonistic activity, but neither document describes the azaindole nor indole derivatives as having DP receptor antagonistic activity.
Furthermore, WO2005/019208 (Patent Document 7) discloses indole derivatives having noradrenaline re-uptake inhibiting activity, and Non-Patent Document 2 discloses indole derivatives having anti-platelet aggregation activity.